Ultrasonic probes provide a convenient and accurate way of gathering information about various structures of interest within a body being analyzed. In general, the various structures of interest have acoustic impedances that are different from the acoustic impedance of a medium of the body surrounding the structures. In operation, such ultrasonic probes generate acoustic waves that are acoustically coupled from the probe into the medium of the body, so that the acoustic waves are transmitted into the body.
For example, medical ultrasonic probes provide a convenient and accurate way for a physician to collect imaging data of various anatomical parts, such as heart tissue or fetal tissue structures within a body of a patient. In general, the heart or fetal tissues of interest have acoustic impedances that are different than an acoustic impedance of bodily fluids surrounding the tissue structures.
In some previously known invasive probes, such as some previously known catheter-type probes capable of imaging inside of a blood vessel or artery, acoustic coupling is achieved by inserting a portion of the probe into the patient's body and through an incision of the blood vessel or artery. For example the probe includes a probe housing, which is inserted into the patients body. The probe housing contains an piezoelectric transducer that generates a beam of ultrasonic acoustic waves. The beam is transmitted through a wall of the probe housing and scans the interior of the blood vessel.
As the acoustic waves propagate through the body, a portion of the acoustic waves are weakly reflected by the various structures within the body, transmitted through the wall of the housing, and received by the transducer. As the weakly reflected acoustic waves propagate through the transducer, they are electrically sensed by electrodes coupled thereto. By analyzing a relative temporal delay and intensity of the weakly reflected waves received by the transducer, imaging system components that are electrically coupled to the electrodes construct an image from the weakly reflected waves to illustrate spaced relation of the various tissue structures within the patient's body and qualities related to the acoustic impedance of the tissue structures. The physician views the reconstructed image on a display device coupled to the imaging system.
Since the acoustic waves are only weakly reflected by the tissue structures of interest, it is important to try to provide efficient acoustic transmission between the transducer and the body under examination. Such efficient acoustic transmission would insure that strength of the acoustic waves generated by the transducer is not excessively diminished as the waves are transmitted from the transducer into the medium of the body. Additionally, such efficient acoustic transmission would insure that strength of the weakly reflected waves are not excessively diminished as the reflected waves are received by the transducer from the medium of the body.
Furthermore, it is undesirable to insert the transducer into the patients body because the piezoelectric transducer may emit leakage currents inside the body, which could possibly induce life threatening fibrillation when the probe images a coronary artery. Furthermore, extended lengths of wires coupled to the electrodes of the inserted transducer act as antennas, which may receive undesirable radio frequency interference signals that could obscure electrical signals representative of an acoustic image.
What is needed is an apparatus that provides efficient coupling and transmission of a beam of acoustic waves between an ultrasonic transducer and a remotely located body under examination by the beam.